The present invention relates to improvements in the package making art and includes, without limitation, thermoformed bags and thermoformed trays, of the kind that may be used for various consumer products, but are particularly useful for food products which should be kept substantially air tight and free from leakage until the packages are opened for access to the product contents, and which packages are desirably reclosable by zipper means for protection of any remainder of product in the packages.
The indicated art is fairly well developed, but nevertheless is still susceptible of improvements for efficiency and cost effectiveness.
One problem that still exists in the production of the packages from continuous zipper equipped sheet matrial such as film, especially where the film and zipper are separately formed and then joined, resides in the difficulty in dividing the zippered film into package oriented sections, due to the greater mass of the zipper than the film.
Another problem has existed in the attainment of satisfactory sealing of the zipper against leakage where the zipper and the area of the film engaged by the zipper are provided with a weakening means such as a line of serrations which maintains the package closed in a tamper evident manner, but which enables ready opening of the package at the weakening means by legitimate owner/user.